Provided the e-mail address is not your primary e-mail address which is used for logging into My VM and it is associated with your current current VM broadband account you should be able to delete it yourself in My Virginmedia.
If this doesn't work or you are no longer a VM broadband customer then wait her for a VM Forum Team to pick up the thread - about a week - and they will help you out.
As a Very Insightful Person, I'm here to share my knowledge. I don't work for Virgin Media.
If the email address is on an inactive VM account and should have auto-closed before now, then we can get this sorted out for you. Please reply to my PM (purple envelope, top right) and I'll get back to you 🙂